Hybrid and electric vehicle battery maintenance device

ABSTRACT

The present invention includes a battery pack maintenance device for performing maintenance on battery packs of hybrid and/or electrical vehicles (referred herein generally as electric vehicles). In various embodiments, the device includes one or more loads for connecting to a battery pack for use in discharging the battery pack, and/or charging circuitry for use in charging the battery pack. Optional input/output circuitry can be provided for communicating with circuitry of in the battery pack and/or circuitry of the vehicle.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. provisional patent application Ser. No. 62/620,665, filed Jan. 23, 2018, the present application is also a Continuation-In-Part of U.S. Ser. No. 16/056,991, filed Aug. 7, 2018, which is a Divisional of U.S. Ser. No. 13/827,128, filed Mar. 14, 2013, which claims benefit of U.S. provisional patent application Ser. No. 61/665,555, filed Jun. 28, 2012, the content of which is hereby incorporated by reference in its entirety.

BACKGROUND

The present invention relates to electric vehicles of the type which use battery packs for storing electricity which is used to power the vehicle. This includes both hybrid and purely electric vehicles. More specifically, the present invention relates to the maintenance of such battery packs used in electric vehicles.

Traditionally, automotive vehicles have used internal combustion engines as their power source. However, vehicles which are electrically powered are finding widespread use. Such vehicle can provide increased fuel efficiency and can be operated using alternative energy sources.

Some types of electric vehicles are completely powered using electric motors and electricity. Other types of electric vehicles include an internal combustion engine. The internal combustion engine can be used to generate electricity and supplement the power delivered by the electric motor. These types of vehicles are known as “hybrid” electric vehicles.

Operation of an electric vehicle requires a power source capable of providing large amounts of electricity. Typically, electric vehicles store electricity in large battery packs which consist of a plurality of batteries. These batteries may be formed by a number of individual cells, or may themselves be individual cells, depending on the configuration of the battery and battery pack. The packs are large, replacement can be expensive and they can be difficult to access and maintain.

Another requirement may be to discharge the battery down to a fixed state of charge, say 30%, for safe transport. It is desired to perform this work as quickly as possible and as safely as possible. Further, since this work often occurs outside and away from permanent structures, light weight portability and operation from batteries is required. These large batteries may have a fully charged voltage in the 400 VDC range, and can store as much as 100 KWh. Further, since this is an activity is infrequently performed, an inexpensive solution is desired.

SUMMARY

The present invention includes a battery pack maintenance device for performing maintenance on battery packs of hybrid and/or electrical vehicles (referred herein generally as electric vehicles). In various embodiments, the device includes one or more loads for connecting to a battery pack for use in discharging the battery pack, and/or charging circuitry for use in charging the battery pack. Optional input/output circuitry can be provided for communicating with circuitry of in the battery pack and/or circuitry of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of a battery maintenance device in accordance with the present invention coupled to an electric vehicle.

FIG. 2 is a more detailed block diagram of the battery maintenance device of FIG. 1.

FIG. 3 is an electrical schematic diagram of a controllable load for use in the battery maintenance device of FIG. 2.

FIG. 4 is a diagram which illustrates one example arrangement of components within the battery maintenance device to promote cooling of such components.

FIG. 5 is a diagram of a plug having an additional load resistance.

FIG. 6 is a perspective view of a housing having resistive loading coils in accordance with one embodiment.

FIG. 7 is a schematic diagram of a controllable resistance load.

FIG. 8 is a graph showing power, discharge current and temperature during battery discharge.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Maintenance of automotive vehicles with internal combustion engines is a well-known art. Procedures are known for servicing the internal combustion engine of the vehicles, the drive train, the battery (which is generally used to start the vehicle and operate the electrical devices within the vehicle), and the fuel storage and distribution system. In contrast, widespread use of electrical vehicles is a relatively new phenomenon and there is an ongoing need for improved procedures for performing maintenance on the batteries of such vehicles. For example, when a traditional vehicle with an internal combustion engine is involved in an accident, it is typical to drain the gasoline or other fuel from the vehicle for safety purposes. In contrast, when an electrical vehicle is involved in an accident, the battery pack of the vehicle may contain a relatively large amount of energy, and may even be in a fully charged state. It is not at all apparent how the battery pack can be discharged as there are many different types of battery pack, as well as various techniques used to access the packs. Further, after an accident, systems of the vehicle may not be functioning properly and may prevent maintenance from being performed on the battery pack whereby the battery pack cannot be discharged using normal procedures. In one aspect, the present invention provides an apparatus and method for safely accessing the battery pack of an electrical vehicle and discharges the battery pack. However, the present invention is not limited to this configuration and may be used generally to perform maintenance on the battery pack of an electric vehicle.

The device of the present invention can be used to “de-power” the battery pack of an electric vehicle or provide other maintenance on the battery pack including charging the battery pack. In general, this activity can be problematic for a number of reasons. First, different types of electric vehicles use different types of battery packs. The configuration, voltages, and connection to such packs vary greatly. Further, the vehicle itself typically includes “intelligence” to control the charging and discharging, as well as monitoring the status of the battery pack. Further still, some battery packs themselves include “intelligence” to control the charging and discharging of the battery pack as well as monitor the status of the battery pack. The device of the present invention is capable of interfacing with a databus of the vehicle and/or a databus of the battery pack in order to control and monitor operation of the battery pack. Again, the connection to these databuses varies greatly between vehicles. Further still, the data format and specific data varies between vehicles. The problem of performing maintenance on a battery pack is exacerbated when a vehicle has been in an accident. The battery pack may be physically difficult to access and it may be difficult to obtain electrical connections to the battery pack and/or vehicle for discharging the battery as well as for communicating over the vehicle or battery pack databus. Depending on the damage which occurs during an accident, the battery pack may be isolated for safety reasons. This isolation presents another challenge in accessing the battery pack. Further, the circuitry of the maintenance device must be capable of operating with the relatively high DC voltages, for example 400 Volts, which are present in electrical vehicle battery packs. These high voltages must be isolated from the logic and control circuitry of the device as well as the operator. Additionally, in one aspect, the device also includes a charger function for use in charging some or all of the cells of a battery pack in order to place the battery pack into service.

Electric vehicles typically includes “contactors” which are electrically operated relays (switches) used to selectively couple the high voltage from the battery pack to the powerful electric motors used in the drive train of the vehicle. In order to access the battery pack from a location on the vehicle, it is necessary for these contactors to be closed to complete the electrical circuit. However, in an accident, the controlling electronics of the vehicle and/or battery pack will typically disconnect (open) the contactors for safety purposes in order to isolate the battery pack from the vehicle. Thus, in one embodiment, the present invention communicates with the controller of the electrical vehicle or battery pack, or directly with the contactors, to cause the contactors to close and thereby provide access to the high voltage of the battery pack. When communicating with the control system of the vehicle, the device of the present invention can provide information to the vehicle system indicating that it is appropriate for the contactors to close. Thus, failure indications or other errors, including errors associated with a vehicle being in an accident, must be suppressed. Instead, information is provided to the vehicle system by the battery pack maintenance device which indicates that it is appropriate for the contactors to be closed.

FIG. 1 is a simplified block diagram showing battery pack maintenance device 100 coupled to an electric vehicle 102. The vehicle 102 is illustrated in a simple block diagram and includes a battery pack 104 used to power the vehicle 102 including providing power to motor(s) 106 of the vehicle. The vehicle 102 includes a vehicle controller 108 coupled to a databus 110 of the vehicle. The controller 108 receives information regarding operation of the vehicle through sensors 112 and controls operation of the vehicle through outputs 114. Further, the battery pack 104 is illustrated as including its own optional controller 120 which monitors operation of the battery pack 104 using battery pack sensors 122.

During operation, the electric vehicle 102 is controlled by the controller 108, for example, based upon input from a driver through operator I/O 109. Operator I/O 109 can comprise, for example, a foot accelerator input, a brake input, an input indicating an position of a steering wheel, information related to a desired gearing ratio for a drive train, outputs related to operation of the vehicle such as speed, charging information, amount of energy which remains in the battery pack 104, diagnostic information, etc. The controller 108 can control operation of the electric motors 106 to propel the vehicle, as well as monitor and control other systems of the vehicle 102. The controller 120 of battery pack 104 can be used to monitor the operation of the battery pack 104. For example, the sensors 122 may include temperature sensors configured to disconnect the batteries of the battery pack if a threshold temperature is exceeded. Other example sensors include current or voltage sensors, which can be used to monitor charge of the battery pack 104. FIG. 1 also illustrates contactor relays 130 of the vehicle 102 which are used to selectively decouple the battery pack 104 from systems of the vehicle 102 as discussed above. For example, the controller 108 can provide a signal to cause the contactors 130 to close thereby connecting the battery pack 104 to electrical systems of the vehicle 102.

Battery pack maintenance device 100 includes a main unit 150 which couples to the vehicle through a low voltage junction box 152 and a high voltage junction box 154. These junction boxes 152, 154 are optional and other techniques may be used for coupling the maintenance device 100 to the vehicle 102. Maintenance device 100 includes a microprocessor 160, I/O circuitry 162 and memory 164 which contains, for example, programming instructions for use by microprocessor 160. The I/O circuitry 162 can be used to both user input, output, remote input, output as well as input and output with vehicle 102. The maintenance device 100 includes a controllable load 170 for use in discharging the battery pack 104. An optional charging source 171 is also provided and can be used in situations in which it is desirable to charge the battery pack 104, for example, to perform maintenance on the battery pack 104. The high voltage junction box 154 is used to provide an electrical connection between terminals of the battery pack 104 and the maintenance device main unit 150. Using this connection, batteries within the battery pack 104 can be discharged using the load 170 or charged using the charging source 171. Similarly, low voltage junction box 152 is used by battery pack maintenance device 100 to couple to low voltage systems of the electric vehicle 102. Such systems include the databus 110 of the vehicle, sensors 112, outputs 114, etc. Through this connection, as discussed above, the maintenance device 100 can gather information regarding the condition of systems within the vehicle 102 including the battery pack 104, and can control operation of systems within the vehicle 102. Similarly, through this connection, the outputs from sensors 112 can be changed or altered whereby altered sensor outputs can be provided to controller 108. This can be used, for example, to cause controller 108 to receive information indicating that the vehicle 102 or battery pack 104 is in a condition which is different than from what the sensors 112 are actually sensing. For example, this connection can be used to cause the contactors 130 to close to thereby provide an electrical connection to the battery pack 104. Further, the low voltage junction box 152 can be used to couple to the controller 120 and/or sensors 122 of the battery pack 104. The junction boxes 152, 154 couple to vehicle 102 through the use of an appropriate connector. The particular connector which is used can be selected based upon the specific type of vehicle 102 and the type of connections which are available to an operator. For example, OBD II connection can be used to couple to the databus 110 of the vehicle. Other plugs or adapters may be used to couple to sensors 112 or outputs 114. A particularly style plug may be available for coupling the high voltage junction box 154 to the battery pack 104. If there are no contactors which are available or if they cannot be accessed or are unresponsive, in one configuration clips or other types of clamp on or selectively connectable contactors can be used to perform the coupling.

FIG. 2 is a simplified block diagram of a battery pack maintenance device 100 in accordance with one example embodiment of the present invention. The device includes microprocessor 160 which operates in accordance with instructions stored in a memory 164. A power supply is used to provide power to the device. The power supply 180 can be coupled to an AC power source, such as a wall outlet or other high power source, for use in charging the battery pack 104 of the vehicle 102. Additionally, the power supply 180 can be coupled to a DC power source, such as a 12 Volt battery, if the device 100 is only used for discharging of the vehicle battery pack 104. For example, in addition to the battery pack 104, many electric vehicles also include a standard 12 Volt automotive battery. This 12 Volt automotive battery can be used to power maintenance device 100. The microprocessor communicates with an operator using an operator input/output 182. Other input/output circuitry 184 is provided for use in physically connecting to a data communication link such as an RS232, USB connection, Ethernet, etc. An optional wireless I/O circuit 186 is also provided for use in communicating in accordance with wireless technologies such as WiFi techniques, Bluetooth®, Zigbee®, etc. Low voltage input/output circuitry 190 is provided for use in communicating with the databus of the vehicle 108, the databus of the battery pack 104, or receiving other inputs or providing outputs to the vehicle 102. Examples include the CAN communication protocol, OBDII, etc. Additionally, contact closures or other voltage inputs or outputs can be applied to the vehicle using the low voltage I/O circuitry 190. FIG. 2 also illustrates an operator shut off switch 192 which can be activated to immediately disconnect the high voltage control 170 from the battery 104 using disconnect switch 194. Other circuit configurations can be used to implement this shut off capability. This configuration allows an operator to perform an emergency shut off or otherwise immediately disconnect the device 100 from the battery if desired.

The low voltage junction box 152 also provides an optional power output. This power can be used, for example, to power components of the vehicle 102 if the vehicle 102 has lost power. This can be useful, for example, to provide power to the controller 108 of the vehicle 102 such that information may be gathered from the vehicle and various components of the vehicle can be controlled such as the contactors 130.

In one configuration, the connection between the high voltage control circuitry 170 and the high voltage junction box 154 is through Kelvin type connectors. This can be used to eliminate the voltage drop which occurs when large currents are drawn through wiring thereby provide more accurate voltage measurements. The actual connection between the junction box 154 and the battery pack 104 need not be through a Kelvin connection if the distance between the junction box 154 and the battery pack 104 is sufficiently short for the voltage drop across the connection leads to be negligible. Isolation circuitry such as fuses may be provided in the junction box 154 to prevent the application of a high voltage or current to the maintenance device 100 and thereby protect circuitry in the device. Similarly, the low voltage junction box 152 and/or the low voltage I/O 190 may include isolation circuitry such as optical isolators, inductors to provide inductive coupling, or other techniques. The low voltage junction box 152 may also include an optional user output and/or input 196. For example, this may be a display which can be observed by an operator. An example display includes an LED display, or individual LEDs, which provides an indication to the operator regarding the functioning of the low voltage junction box, the vehicle, or the battery pack. This can be used to visually inform an operator regarding the various functions being performed by the low voltage junction box, voltages detected by the low voltage junction box. A visual output and/or input 198 can be provided on the high voltage junction box 154.

The appropriate high voltage junction box 154 and low voltage junction box 152 can be selected based upon the particular vehicle 102 or battery pack 104 being inspected. Similarly, the junction boxes 152, 154 can be selected based upon the types of connections which are available in a particular situation. For example, if the vehicle his damaged, it may be impossible to couple to the battery pack 104 through available connectors. Instead, a junction box 154 can be employed which includes connection probes which can be coupled directly to the battery pack 104. Further still, if such a connection is not available or is damaged, connectors can be provided for coupling to individual cells or batteries within the battery pack 104.

The use of the low voltage and high voltage junction boxes 152, 154 are advantageous for a number of reasons. The junction boxes can be used to provide a standardized connection to the circuitry of the maintenance device 100. From a junction box 152, 154, specialized connectors can be provided for use with different types of vehicles and/or battery packs. Similarly, different types of junction boxes 152, 154 can be utilized for different vehicles and/or battery packs. The junction boxes 152, 154 allow a single set cable connection to extend between the device 100 and a remote location. This provides better cable management, ease of use, and increased accuracy.

In addition to use as a load for discharging the battery, the high voltage control circuitry may also optionally include a charging for use in charging the battery.

FIG. 3 is a schematic diagram of controllable load 170. In FIG. 3, a number of isolated gate bipolar transistors (IGBT) 220A, 220B, 220C, and 220D are shown and controlled by a gate connection to microprocessor 160. The IGBTs 220A-D connect to load resistors 222A, 222B, 224A, and 224B. As illustrated in FIG. 3, the four load resistors are 33 OHM resistors. Using the transistors 220A-D, the resistors 222A, B and 224A, B can be coupled in various series-parallel configurations in order to apply different loads to the battery pack 104. In this way, the load applied to the battery pack 104 is controllable by microprocessor 160. In one aspect, the present invention includes isolated gate bipolar transistors (IGBT) to selectively couple loads to the battery pack 104 for discharging the pack. An IGBT is a transistor configured with four semiconducting layers arranged as PNPN. A metal oxide semiconductor is arranged to provide a gate. The configuration provides a transistor which is controlled easily in a manner similar to a field effect transistor but which is also capable of switching large currents like a bipolar transistor.

When the device 100 is coupled to a vehicle 102 which has been in an accident, the device can perform various tests on the vehicle 102 to determine the condition of the vehicle and the battery. For example, in one aspect, the device 100 detects a leakage between the positive and negative terminals of the battery pack 102 and the ground or chassis of the vehicle 102. For example, a wheat stone bridge circuit 230 can be used between the positive and negative terminals of the battery pack 104 with one of the legs of the bridge connected to ground.

During discharging of the vehicle battery pack 104, data can be collected from the battery pack. For example, battery packs typically include sensors 122 such as voltage, current and temperature sensors arranged to collect data from various locations within the battery pack. This information can be obtained by the maintenance device 100 via the coupling to the databus 110. During discharge, any abnormal parameters measured by the sensors can be used to control the discharge. For example, if the battery pack 104 is experiencing excessive heating, the discharge rate can be reduced until the battery temperature returns to an acceptable level. If any of the internal temperature sensors of the battery pack are not functioning, an external battery pack temperature sensor can be used to detect the temperature of the battery pack. Similarly, if cells within the pack are experiencing an abnormally high current discharge, the discharge rate can be reduced. Further still, if such data cannot be obtained because the sensors are damages or the databus is damaged or inaccessible, the maintenance device 100 can automatically enter a slow/safe discharge state to ensure that the battery is not damaged.

When placing a battery pack 104 into service, the maintenance device 100 can identify individual cells or batteries within the pack 104 which are more or less charged than other cells. Thus, the individual cells or batteries within a pack can be balanced whereby they all have substantially the same charge capacity and/or state of charge as the other cells or batteries within the pack.

In another aspect of the present invention, the maintenance device 100 is capable of providing a “jump start” to a hybrid electric vehicle 102. For example, if the internal combustion engine of a hybrid electric vehicle is started using power directly from the battery pack and if the charge of the battery pack 104 is too low, there is insufficient energy available to start the engine. The maintenance device 100 of the present invention can be used to provide sufficient power to a starter motor of the internal combustion engine for starting the engine. Once the internal combustion engine is running, the engine itself is used to charge the battery pack 104.

In FIG. 3, a voltage sensor 232 is connected across the wheat stone bridge 230. Further, the bridge is optionally connected to electrical ground through switch 234. Any voltage detected by voltage sensor 232 across the bridge 230 is an indication that there is a current leak between the positive and/or negative terminals of the battery pack 104 and the electrical ground or chassis of the vehicle 102. The voltage sensor 232 can provide an output to microprocessor 130 and used to alert an operator of a potentially dangerous situation and indicate that the battery pack 104 must be disconnected from the vehicle 102 before further maintenance is performed.

FIG. 3 also illustrates a relay 226 which is used to isolate the load resistances 222/224 from the battery pack until a discharge is commanded by the microprocessor 160. The voltage across the battery pack 104 can be measured using a voltage sensor 242 connected in series with a resistance 240. The output from sensor 242 is provided to microprocessor 160 for use in performing maintenance in the battery pack 104.

During operation, the components of the device 100 may experience a great deal of heating. An air flow cooling system can be used to dissipate the heat. FIG. 4 shows one such configuration. As illustrated in FIG. 4, the air flow moves from the low power electronics 300, passed the high power electronics 302 and over the load resistors 222A, B and 224A, B. The air flow then leaves the housing of the device 100. In FIG. 4, the air flow is controlled by fans 304. The fans 304 can be controlled using microprocessor 160 whereby their speed can be adjusted as needed based upon measurements from temperature sensors 306 which can be placed at various locations within the housing of device 100. In this configuration, hot air generated by the load resistance is immediately blown out of the housing rather than past any components.

Some electrical vehicles include what is referred to as a “pre-charge contactor.” The pre-charge contactor can be used to charge capacitances of the vehicle at a slow and controlled rate prior to switching in the main contactor 130 shown in FIG. 1. This prevents excessive current discharge from the battery pack when the main contactor is activated and the pack is directly coupled to the loads of the vehicle including the traction module of the vehicle which is used to control electric motors of the vehicle.

In another aspect, some or all of the information obtained during testing and discharge of a battery pack 104 is retrieved and stored, for example in the memory 164 shown in FIG. 1, for subsequent access. This information can be offloaded to another device, for example a USB drive or the like, or transmitted over a network connection. This can be particularly useful to examine information retrieved after a vehicle has experienced an accident. The information can be information which is downloaded from the controller 108 of the vehicle 102 and may also be information related to how the vehicle battery pack 104 was discharged and removed of service.

In another aspect, more than one maintenance device 100 can be coupled to a battery pack 104 and the multiple devices can be configured to work in tandem. More specifically, the devices 100 can be coupled using the input/output circuitry 184 shown in FIG. 2 whereby one of the devices 100 operates as a master and one or more other devices 100 operate as slaves under the control of the master device. This arrangement can be used to increase the rate at which a battery pack 104 is discharged. In such a configuration, a bridgeable power supply may also be employed.

FIG. 5 is a simplified diagram showing a removable plug 350 which can be selectively coupled to battery pack maintenance device 100. Removable plug 350 includes a 5 OHM resistor 352 configured to connect in parallel through connectors 354 and 356. Removable plug 350 includes a magnet 360 configured to actuate a reed switch 362. Reed switch 362 connects to microprocessor 160 whereby microprocessor 160 can sense the presence of the plug 350. When plug 350 is coupled to device 100, the resistance of one or more of the 33 OHM resistors 222A,B and 224 A,B can be changed because the resistor is in series with the 5 OHM resistor yielding a resistance of about 4.3 OHMs. However, any configuration desired can be provided. This allows the device 100 to apply a smaller resistance to the battery pack 104 thereby increasing the discharge rate if desired. For example, a particular battery pack may be of a sufficiently low voltage to allow for an increased current draw to thereby increase the rate at which the battery pack 104 is discharged. Using reed switch 362, the microprocessor 160 is able to detect the presence of the plug 350 whereby calculations which rely on the value of applied load resistance can be compensated appropriately. Although only a single resistor 352 is shown, the plug 350 may include any number of resistors to be placed in parallel with load resistances in the device 100. Preferably plug 350 includes a cooling mechanism to reduce the heating of resistor 352. For example, the plug 350 may include metal or other heat conducting fins or the like. A fan may also be employed. The fan may be the same cooling fan used in device 100 or, plug 350 may optionally include its own fan. In another embodiment, the alternative resistance values are located within the main unit, and are switched into circuit using the removable plug.

FIG. 6 is a perspective view of another example embodiment of a controllable load 170 illustrated in a housing 402. In the configuration of FIG. 6, resistive elements are provided using a number of resistive coils 400. In one example embodiment, these resistive coils can be the type of coils used in consumer applications such as electric clothing dryers. For example, one such coil is rated at approximately 5.3 KW at 240 volts. Note that if the rated voltage is exceeded, the coil will melt and become an open circuit. Further, it is also preferable that the coils 400 have resistances which are similar. The coils 400 are carried on supports 404 preferably made of an electric insulator capable of handling high temperatures. To assist in heat dissipation, an air flow can be provided across the coils 400 as shown in FIG. 4.

FIG. 7 is a simplified schematic diagram of another example embodiment of controllable load 100. In the configuration of FIG. 7, the four coils 400 illustrated in FIG. 6 are electrically connected in a series/parallel configuration. In this configuration, switches K1, K2, K3 and K4 are provided for controlling the resistance provided by controllable load 100. These switches can be any type of switch including relays or transistor switches. In one configuration, the switches are manual switches. Switches K1 and K2 control two parallel legs of the circuit while switches K3 and K4 control the amount of resistance in series in each leg. In this configuration, a maximum discharge capability of 20 KW is provided if both switches K1 and K2 are closed and switches K3 and K4 are open. The B+ and B− connections are used for coupling to the storage battery and fusible links 406 are provided for safety. In one example configuration, if the voltage across terminals B+ and B− drops below 240 volts DC, switch K3 and/or switch K4 can then be closed to reduce the resistance applied to battery 104 and optimize the loading of the battery. FIG. 8 is a graph showing the loading performance of such an arrangement. As illustrated in FIG. 8, the step change occurs when the resistive load provided by controllable load 100 is decreased, for example, by activating switch K2

As mentioned above, the fans illustrated in FIG. 4 can be used to provide an air flow across the coils 400. In one configuration, all of the fans control circuits and relays may be operated by 12 volt DC and can be powered, for example, by an auxiliary battery or a “cigarette lighter” output from a vehicle such as a tow truck. A double insulation technique can be used proximate the load coils such that any electrical fault, for example a heater coil failure, cannot be conducted to a location outside of the housing 402. Optional temperature safety sensors 306 shown in FIG. 4 can be used. The temperature sensors 306 can be provided on both the inlet and the outlet of each heater coil and can be used to detect fan failure or blocked air flow. This configuration can also be used to detect the amount that the air is heated by the coil. In another example configuration, fusible links 404 may provide hard wired temperature cutout switches to prevent overheating. In such a configuration, when a temperature threshold is reached, the switch will open. Data obtained during discharge can be logged to a memory such as memory 164 such as a local flash drive or other local storage device. In another configuration, the logged data is sent to a remote location such as cloud storage for analysis. Such records can be of significance for warranty or insurance purposes.

In one configuration, the voltage sensor 232 is used to detect leakage currents in the battery undergoing discharge. The device can also monitor battery cell voltages and temperatures to ensure that unsafe conditions are not being created during discharge.

The input/output circuitry 190 can be used to connect to a databus of the vehicle, for example, through an OBDII connection in order to collect information such as VIN, software and hardware version numbers, etc. The device can communicate with the battery ECU (Electronic Control Unit) using any appropriate protocol including CAN, LIN, or others, in order to obtain specific battery information and discharge protocols. The device can be connected as a slave unit to another piece of shop equipment either using a hardwire connection or a wireless connection such as Bluetooth or Wi-Fi. Reverse polarity protection as well as overvoltage protection can be provided. Other safety techniques for electrical potential, temperature and axis points can be fully interlocked to prevent operation of the unit. In one configuration, the input/output 184 can include a barcode scanner which can then be used to capture specific information such as battery type or serial number as well as vehicle identification number, etc. In another example configuration, input/output circuitry 184 can include a remote temperature sensor that can be electrically coupled to the discharger to report battery temperature. This is useful when internal battery temperature sensors are damaged or inoperative. The devices are scalable such that multiple controllable loads 100 can be connected in parallel. Relay contacts can also be provided and available externally to control various circuits on the battery pack undergoing discharge. Additional voltage sensing connections such as those provided by junction box 152 can be used to monitor various circuits on the battery pack.

Another example configuration includes a high voltage DC to DC converter such as power supply 180 shown in FIG. 2. In such a configuration, the high voltage output from the battery pack can be converted to a lower DC voltage for use in powering the device.

As discussed above, in some configurations the present invention can be arranged to measure a dynamic parameter of the battery pack. In such a configuration, a forcing function is applied to the battery pack and a dynamic parameter such as dynamic conductance, resistance, admittance, etc. can be determined based upon a change in the voltage across the battery pack and the current flowing through the battery pack. The forcing function can be any type of function which has a time varying aspect including an AC signal or a transient signal.

In one aspect, the maintenance device can be configured to “balance” individual cells within the battery pack. The balancing can be performed by selected cells or individual batteries within the pack which have similar storage capacity and state of charge. The charging feature of the device can be used to increase the charge of a cell or battery to that of other cells or batteries. Similarly, the maintenance device can be used to discharge individual cells or batteries to a level similar to that of other cells or batteries within the pack.

In another aspect, the device of FIG. 1 includes an ambient temperature sensor. The microprocessor can use information from the ambient temperature sensor in determining how the battery pack should be discharged. For example, if the ambient temperature is high, the discharge rate can be reduced.

During discharge of the battery pack, the discharge profile can be monitored to ensure proper operation. For example, if the voltage of the battery suddenly drops, this can be an indication that a component within the battery has failed or a short circuit has occurred.

Different types of junction boxes and connection cables can be used based upon the particular type of vehicle and battery pack under maintenance. The microprocessor can provide information to the operator prompting the operator to use the appropriate junction box or cable. This can be based upon the operator inputting the vehicle identification number (VIN) to the microprocessor, or other identifying information including an identification number associated with the battery pack. During discharging of the battery pack, the microprocessor can also provide information to the operator which indicates the time remaining to complete the discharge. The microprocessor 160 can also detect if the correct junction box and cable have been coupled to the device and to the battery pack for the particular battery pack and vehicle under maintenance. Information can be provided to the operator if the wrong cabling or junction box has been employed.

The device of the present invention can be used with battery packs which have been removed from a vehicle as well as individual batteries, or groups of batteries, within a pack. For example, a battery pack typically includes a battery connector assembly which is used by the vehicle 102 to couple to the battery pack 104. However, when the battery pack 104 is removed from the vehicle 102, the device 100 can directly couple to this battery connector assembly and thereby charge or discharge the battery pack, perform tests on the battery pack, interact with devices on the battery pack including sensors, controllers, etc. As discussed above, the device 100 can include multiple connectors for use in connecting the low voltage junction box 152 and/or the high voltage junction box 154 to the vehicle 102 and/or battery pack 104. This allows the device 100 to easily be modified to interact with different types of batteries or vehicles by simply selecting the appropriate connector. In one configuration, the connectors include some type of identifier which can be read by the device 100 whereby the microprocessor 160 and device 100 can receive information to thereby identify the type of connector in use. This allows the microprocessor 100 to know what types of information or tests may be available through the various connectors. In another example, the operator uses operator I/O 182 shown in FIG. 2 to input information to the microprocessor 160 related to the type of connector(s) being used. In another example embodiment, the microprocessor 160 may receive information which identifies the type of vehicle or battery on which maintenance is being performed. This information can be input by an operator using the operator I/O 182, or through some other means such as by communicating with the databus of the vehicle, scanning a barcode or other type of input, etc. Based upon this information, the microprocessor can provide an output to the operator using operator I/O 182 which informs the operator which type of interconnect cable should be used to couple the low voltage junction box 152 and/or the high voltage junction box 154 to the vehicle and/or battery pack.

The operator I/O 182 may include a display along with a keypad input or touchscreen. The input may take various formats, for example, a menu driven format in which an operator moves through a series of menus selecting various options and configurations. Similarly, the operator I/O 182 can be used by the microprocessor 160 to step the operator through a maintenance procedure. In one configuration, the memory 164 is configured to receive a user identification which identifies the operator using the equipment. This can be input, for example, through operator I/O 182 and allows information related to the maintenance being performed to be associated with information which identifies a particular operator. Additional information that can be associated with the maintenance data include tests performed on the vehicle and/or battery, logging information, steps performed in accordance with the maintenance, date and time information, geographical location information, environmental information including temperature, test conditions, etc., along with any other desired information. This information can be stored in memory 164 for concurrent or subsequent transmission to another device or location for further analysis. Memory 164 can also store program instructions, battery parameters, vehicle parameters, testing or maintenance information or procedures, as well as other information. These programming instructions can be updated, for example, using I/O 184 or 186, through an USB flash drive, SD card or other memory device, or through some other means as desired. This allows the device 100 to be modified, for example, if new types of vehicles or battery pack configurations are released, if new testing or maintenance procedures are desired, etc.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. Techniques useful for implementing the invention can be found in U.S. Pat. No. 3,873,911, issued Mar. 25, 1975, to Champlin; U.S. Pat. No. 3,909,708, issued Sep. 30, 1975, to Champlin; U.S. Pat. No. 4,816,768, issued Mar. 28, 1989, to Champlin; U.S. Pat. No. 4,825,170, issued Apr. 25, 1989, to Champlin; U.S. Pat. No. 4,881,038, issued Nov. 14, 1989, to Champlin; U.S. Pat. No. 4,912,416, issued Mar. 27, 1990, to Champlin; U.S. Pat. No. 5,140,269, issued Aug. 18, 1992, to Champlin; U.S. Pat. No. 5,343,380, issued Aug. 30, 1994; U.S. Pat. No. 5,572,136, issued Nov. 5, 1996; U.S. Pat. No. 5,574,355, issued Nov. 12, 1996; U.S. Pat. No. 5,583,416, issued Dec. 10, 1996; U.S. Pat. No. 5,585,728, issued Dec. 17, 1996; U.S. Pat. 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What is claimed is:
 1. A maintenance device for coupling to a battery of an electric vehicle and performing maintenance on the battery, comprising: a device housing; a controller in the housing configured to control operation of the maintenance device; a controllable load including a plurality of resistive wire loading coils configured to apply a resistive discharge load to the battery to draw a DC current from the battery and perform maintenance on the battery, the controllable load comprising: a first parallel leg comprising: a first coil; a second coil electrically connected in series with the first coil; a first switch configured to selectively couple the first parallel leg to the battery; a second switch configured to selectively provide an electrical short across the second coil; a second parallel leg electrically connected in parallel with the first parallel leg comprising: a third coil; a fourth coil electrically connected in series with the third coil; a third switch configured to selectively couple the second parallel leg to the battery; a fourth switch configured to selectively provide an electrical short across the fourth coil; and load control circuitry configured to selectively couple the plurality of resistive wire loading coils to the battery in response to an output from the controller whereby the load control circuitry is configured to selectively couple a single resistive wire loading coil to the battery and selectively couple a plurality of resistive wire loading coils to the battery to achieve a desired resistive load applied to the battery by selectively activating the first, second, third and fourth switches.
 2. The apparatus of claim 1 including a junction box configured to couple the controllable load to the battery.
 3. The apparatus of claim 1 including communication circuitry configured to couple to a databus of the electric vehicle.
 4. The apparatus of claim 1 including communication circuitry configured to couple to the battery pack which contains the battery of the electric vehicle.
 5. The apparatus of claim 1 including power supply circuitry configured to be powered by a 12 volt source.
 6. The apparatus of claim 1 including a shut off switch configured to be actuated by an operator which disconnects the controllable load from the battery.
 7. The apparatus of claim 1 including an insulated gate bipolar transistor coupled to each of the plurality of wire loading coils.
 8. The apparatus of claim 1 including a junction box configured to couple the controller to a databus of the vehicle.
 9. The apparatus of claim 1 including a bridge circuit configured to couple to the battery and wherein a voltage difference across the bridge circuit is indicative of electrical current leakage from the battery to electrical ground.
 10. The apparatus of claim 1 wherein the controller is configured to communicate with a databus of the electric vehicle during discharge of the battery.
 11. A slave device configured to couple to the apparatus of claim 1 the slave device including a slave controllable load configured to apply a slave load to the battery.
 12. The apparatus of claim 11 wherein the controller controls the slave controllable load to thereby apply a total load which is lesser than the controllable load.
 13. The apparatus of claim 1 wherein the controller is electrically isolated from the controllable load.
 14. The apparatus of claim 1 including a memory configured to log information related to discharging of the battery.
 15. The apparatus of claim 1 further including charge circuitry configured to electrically charge a cell or battery of the battery.
 16. The apparatus of claim 1 wherein the controllable load includes at least two load resistances configured to the selectively electrically coupled to the battery. 